This subclass is used for dicts with guaranteed values of children but can still be used like a normal dict.

suredict.py

class SureDict(dict):
    """
    This subclass is used for dicts with guaranteed values of children but
    can still be used like a normal dict.

    .. note::

        Note that only the top level will be of class SureDict, those children
        whose values are of dict will remain dict.

    Example::

        >>> a_dict = {
        ...     'aKey': 'a value',
        ...     'top': {
        ...         'child1': 'child2 is a dict',
        ...         'child2': {
        ...             'grandSon': 'this is a boy',
        ...             'grandDaughter': 'this is a girl'
        ...         }
        ...     }
        ... }
        >>> a_dict.get('top:child1')
        >>> a_dict.get('top:child1', 'Nothing')
        'Nothing'
        >>> sure_dict = SureDict(a_dict)
        >>> sure_dict.get('top:child1')
        'child2 is a dict'
        >>> sure_dict.get('top:child2:grandSon')
        'this is a boy'
        >>> sure_dict.get('top:child2:grandDaughter')
        'this is a girl'
        >>> sure_dict.get('top:child2:grandMother')
        >>> sure_dict.get('top:child2:grandMother', 'Nothing')
        'Nothing'
        >>> child_dict = sure_dict.get('top')
        >>> child_dict.get('child2')
        {'grandSon': 'this is a boy', 'grandDaughter': 'this is a girl'}
        >>> child_dict.get('child2:grandSon')
        >>> child_dict.get('child2:grandSon', 'Nothing')
        'Nothing'
    """

    def get(self, k, d=None):
        assert type(k) is str, "Keys must be strings."
        keys = k.split(":")

        _last_key = keys.pop(0)
        value = super().get(_last_key, d)

        for key in keys:
            assert isinstance(value,
                              dict), "Expected dict for child of '%s' key but" \
                                     " got the value '%s' instead." % (
                                         _last_key, value)
            value = value.get(key, d)

        return value